ibroblasts and endothelial cells both are capable of the hagocytosis and degradation of mass cell granules as emonstrated by microscopy and by the use of radiolabeled mast ell granules. The degradation of heparin proteoglycan follows he exposure of this molecule to reactive radicals formed as a onsequence of the respiratory burst. This process is rapid nd results in heparin proteoglycan products that appear imilar to the heparin fragments found in commercial reparations of heparin. ast cell granules rapidly degrade extracellular fibronectin. hile this degradation is probably due to chymase, mast cell ranules are particularly efficient at cleaving fibronectin. his may represent a major extracellular function of mast cell ranules and influence repair mechanisms within connective issues. asophils from human cord blood synthesize chondroitin -sulfate, a molecule previously identified in mature human asophils. he induction of autoimmune uveitis is associated with horoidal mast cell numbers in a rat model of this disease. roteoglycan heparin is rapidly degraded following exposure to eactive radicals formed during the respiratory burst. The roducts have an approximate molecular weight of 12,000, which s similar to the size of heparins in commercial preparations. his observation may explain how phagocytic cells are able to apidly degrade proteoglycan heparin and mast cell granules.